Plasma Chemistry and Plasma Processing, Vol. 18, No. 3, 1998
Solid-Phase Synthesis of Calcium Carbide in a
Plasma Reactor
M. H. El-Naas,1 R. J. Munz,1 and F. Ajersch2
Received August 17, 1996; revised December 4, 1997
A laboratory-scale spout-fluid bed reactor with a dc plasma torch was used to study
the solid-phase synthesis of calcium carbide. Calcium oxide powder with a mean
particle size of 170 um was reacted with graphite powder (130 um). Argon was
used to initiate the plasma and hydrogen gas was then added to increase power and
raise the plasma jet enthalpy. Experimental results showed that the reaction took
place in the vicinity of the plasma jet and that conversion to calcium carbide
increased linearly with reaction time. The rate of conversion increased exponentially
with plasma jet temperature, indicating that chemical reaction was the controlling
mechanism. Microscopic analysis of the solid product showed that calcium carbide
was formed around both reactants, and that the reaction followed a shrinking core
model. Although melting and agglomeration of partially reacted particles occurred
at high temperature, resulting in instability of the bed and impeding the reaction
progress, high conversions are expected in a continuous process with optimized
reactor design.
KEY WORDS: Calcium carbide; solid-phase synthesis; plasma synthesis; plasma
process; plasma spout-fluid bed; solid-phase reactions.
1. INTRODUCTION
Calcium carbide is an important industrial commodity. Its growing
industrial applications in the desulfurization of steel and cast iron and in
the production of acetylene and cyanamide have given it great importance
as a chemical and further enhanced commercial interest in its production.
Calcium carbide is presently produced by reacting calcium oxide and carbon
in large electric arc furnaces at about 2400 K. The molten product is tapped
from the furnace at about 2073 K, cooled, cast, and then crushed and ground
to the size required for marketing. The energy consumption for a typical
electric arc furnace is of the order of 4 kWh/kg CaC2. Several methods,
1CRTP,
Department of Chemical Engineering, McGill University, 3610 University St., Montreal, Quebec H3A 2B2, Canada.
2Departement de Metallurgie et de Genie des materiaux, Ecole Polytechnique, C.P. 6079 Succ.
Centre-ville, Montreal, Quebec H3C 3A7, Canada.
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0272-4324/98/0900-0409$15.00/0 © 1998 Plenum Publishing Corporation
410
El-Nans, Munz, and Ajersch
aiming at developing a more efficient process, have been studied for the
production of calcium carbide using different furnace designs and different
heating mechanisms.(1-4) Baba and Shohata(1) and Eriksson(2) patented processes using high-frequency plasma for the production of calcium carbide.
Both processes, however, have an energy consumption that is much higher
than that of the present electric arc furnace.
Calcium carbide is formed by reacting calcium oxide and carbon according to the following reaction
This reaction is believed to proceed according to the following two-step
mechanism first proposed by Kameyama(12)
Tagawa and Sugawara(13) studied the solid-phase reaction of carbon and
calcium oxide in pellets and found that the two solid reactants formed a
solid interstate compound CaO • C at temperatures above 1273 K, where
the diffusion of carbon into calcium oxide and vice versa was believed to be
the controlling step. Mukaibo and Yamanka(14) studied the kinetics of
reaction (2) by heating pellets of calcium oxide and carbon between 1473
and 1673 K under vacuum. They found the reaction to be zero-order and
the reaction rate rather than diffusion to the rate-limiting step.
Reaction (3) is an essential step in the formation of calcium carbide
through the surface reaction of calcium vapor and carbon. However, the
mechanism by which calcium vapor and carbon monoxide are formed in a
solid-phase reaction is not well understood. Hellmold and Gordziel(15) and
Muller(16) discussed the idea of ionic diffusion as a means of carbon transport
into the CaO lattice and of reducing the oxide to Ca(g). According to
Muller,(l7) it is the role of the carbon materials to provide the C3 molecules
to initiate the ionization, form another "interstate" compound (CaC3O),
and eventually form calcium vapor. Once formed, calcium vapor reacts with
either the diffused carbon at the surface of the oxide or with the free carbon
to form calcium carbide. It is this surface reaction (3) that is believed to
control the overall rate of formation of calcium carbide.
A new plasma process has been studied to replace the present electric
arc furnace. In this new process, the reaction between calcium oxide and
carbon takes place in the solid phase in a plasma fluid bed reactor. Plasma
fluidized and spouted beds have been studied extensively in the past thirty
years.(5-10) The combination of high plasma temperature and the good mixing associated with fluidization make plasma fluidized beds ideal for the
Solid-Phase Synthesis of Calcium Carbide in a Plasma Reactor
411
highly endothermic gas-solid and solid-solid reactions. A thermodynamic
analysis of the formation of calcium carbide in a plasma fluidized bed predicted that the reaction would be completed at 2150 K and that the plasma
process could lower the energy consumption by up to 40%.(11) The use of a
solid-state reaction with fine particle reactants will produce a granular product and thus avoid the cost of grinding associated with the electric arc
process. Also, the sensible heat of the products can be recovered to heat the
reactants and hence lower the energy requirements.
2. EXPERIMENTAL METHODS
The experimental apparatus consisted of a power supply, a dc plasma
torch, a fluid bed, a CO analyzer, and a temperature measuring system as
shown schematically in Fig. 1. The plasma torch was composed of a conical
thoriated tungsten cathode and an annular copper anode, with a design
power of the order of 20 kW. Power to the torch was controlled by varying
the current and the plasma gas composition. The fluid bed system consisted
of two parts: the reactor section and the disengaging section. The inner part
of the reactor was lined with a graphite cylinder (8 cm in internal diameter
and 35 cm in height) surrounded by 2 cm of graphite felt insulation. Both
the graphite cylinder and the felt were contained within a stainless steel
cylinder (13 cm in internal diameter) which was also insulated on the outside
Fig. 1. A schematic diagram of the experimental apparatus.
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El-Naas, Munz, and Ajersch
Fig. 2. A detailed representation of the fluid bed reactor.
to minimize heat loss. The lower part of the reactor housed the distributor
and the plasma torch. The stainless steel disengaging section measured 25 cm
in internal diameter and 25 cm in height. The large diameter lowered the
gas velocity and minimized elutriation of particles. A detailed representation
of the fluid bed reactor is shown in Fig. 2.
Argon at a flow rate of 40 L/min was used to initiate the arc, and
hydrogen was subsequently added to increase the arc voltage and hence raise
the power and plasma enthalpy. Three different levels of hydrogen content
were used in the experiments (33,45, and 67 vol.%). Argon was also used
to fluidize the bed at just above the minimum fluidization velocity. The bed
temperature ranged from ambient to about 1573 K and was measured using
Accufiber High Temperature Measurement and Control System Model
Solid-Phase Synthesis of Calcium Carbide in a Plasma Reactor
413
100C. Calcium oxide powder with a mean particle size of 170 um was reacted
with graphite powder (130um). The reactants were charged into the batch
reactor at a stoichiometric ratio of 3 C to 1 CaO with a total mass of 1 kg.
The gaseous products leave the reactor with the plasma gas, where they pass
through a heat exchanger and a baghouse filter before evacuation into a
fume hood. The gases were continuously analyzed for carbon monoxide
using a Horiba Mexa-201GE CO analyzer.
3. RESULTS AND DISCUSSION
3.1. Effect of Plasma Jet Temperature
Argon at a flow rate of 40 L/min was used to initiate the arc and start
the plasma torch. The maximum power that was achieved with argon
plasma, however, was too low to provide a temperature high enough for
good conversion to calcium carbide. Hydrogen was then added to the plasma
gas to increase the arc voltage and hence raise the plasma power. For a
fixed current (240 A), the arc voltage increased with hydrogen addition,
resulting in a power increase from 5 kW with pure argon to 18 kW with
67% hydrogen. Hydrogen addition increases the power as well as the thermal
conductivity and the heat capacity of the plasma gas. Both the enthalpy and
the temperature of the plasma jet are increased as the hydrogen content is
increased at constant current. The jet temperature was calculated by performing an energy balance with a torch efficiency of 60%, measured
experimentally.
While keeping the current fixed at 240 A, experiments were conducted
for different plasma powers by varying the hydrogen concentration in the
plasma gas. Figure 3 shows a plot of the integral conversion of calcium
oxide as a function of run time for four plasma gas compositions (H 2 ,
vol.% in Ar): 0%, 33%, 45%, and 67%. Conversion was calculated from the
cumulative total quantity of carbon monoxide measured experimentally.
Thus, conversion at any time was calculated as the moles of carbon monoxide
produced per mole of calcium oxide initially fed to the reactor. It can be clearly
observed that the conversion increased linearly with time, and the rate of
conversion increased with plasma power or hydrogen concentration in the
plasma gas. The rate of conversion at any time represented the instantaneous
global rate of reaction. This rate was found to be constant with time for a
fixed power (fixed plasma jet temperature) and increased exponentially with
increasing plasma jet temperature as is shown in Fig. 4. The reaction rates
at different conditions are shown in Table I. One would expect the rate of
conversion to increase with time, since the bed was heating up and the bed
temperature was increasing with the run time as shown in Fig. 5. The fact
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El-Naas, Munz, and Ajersch
Fig. 3. Conversion of calcium oxide to carbon monoxide as a function of run time for different
plasma powers. Carbon to calcium oxide molar ratio was 3:1 and plasma gas flow rate was
40 L/min.
that the rate was constant indicated that the change in reaction temperature
with time for the duration of the experimental run was negligible. A plot of
conversion vs. bed temperature for different conditions is shown in Fig. 6.
The highest conversion (30%) occurred at a bed temperature of 1573 K,
which is less than the temperature required thermodynamically for the
reaction to proceed. This clearly indicated that the reaction between calcium
oxide and graphite did not take place in the bed, but in the vicinity of the
plasma jet where the temperature was sufficiently high for the reaction to
occur. Thus, the fluid bed reactor is assumed to consist of two different
zones: a high-temperature reaction zone and a well-mixed isothermal bed
zone. The size of the reaction zone depends on the plasma conditions and
is proportional to the plasma jet enthalpy. The bed zone, which represents
most of the reactor volume, acts as a mixing zone that feeds particles into
415
Solid-Phase Synthesis of Calcium Carbide in a Plasma Reactor
Fig. 4. Rate of conversion vs. calculated plasma jet temperature.
Table I. Reaction Rates at Different Conditions
H2
(vol.%)
Power
(kW)
Calculated
Tjet (K)
Reaction rate
(mol/min)
0
33
45
67
5
12
14
18
8400
9400
9800
10200
0.006
0.026
0.042
0.091
the jet zone where they react. A model of the plasma reactor with the two
zones is described in detail in a recent publication.(18)
As particles enter the reaction zone, their temperature rises from the
bed temperature to a maximum particle temperature. Except for the first 45 min of each run, the rate of increase in the bed temperature is relatively
small. On the other hand, the increase of the particle temperature is very
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El-Naas, Munz, and Ajersch
Fig. 5. Bed temperature vs. run time for different plasma powers. Plasma gas flow rate was
40 L/min and current was 240 A.
high as the particles pass through the reaction zone. Thus, the difference in
the bed temperature for the entire run is much smaller than the particle
temperature increase in the jet. As a result, the particle temperature, which
determines the surface reaction temperature, is almost constant with time
and explains the constant rate of reaction despite the continuous heating of
the bed.
3.2. Effect of Hydrogen Addition
The plasma power could be varied by either changing the current while
fixing the plasma gas composition, or by varying hydrogen concentration
while fixing current. The overall effect of increasing power by either mechanism is increasing the plasma jet enthalpy and hence plasma jet temperature.
It is expected that hydrogen addition affects the reaction rate by raising
Solid-Phase Synthesis of Calcium Carbide in a Plasma Reactor
417
Fig. 6. Conversion of calcium oxide to carbon monoxide vs. bed temperature at different
plasma powers. Carbon to calcium oxide molar ratio was 3:1 and plasma gas flow rate was
40 L/min.
plasma power and enthalpy and not by involvement in the reaction. To
verify this point, hydrogen concentration was kept constant at 33%, while
power was increased by raising the current to equal the power of 45%
hydrogen. A plot of conversion vs. run time for the three cases is shown in
Fig. 7. It can be observed that for the same power input the rate of conversion was about the same for different hydrogen concentrations. This implies
that hydrogen affects the rate only by raising the plasma power and plasma
jet enthalpy.
The influence of an instantaneous reaction zone temperature change on
the rate of conversion was further investigated by injecting methane into the
jet and by lowering the current. This was carried out for a plasma gas
composition of 67% hydrogen. In the first run, methane was injected after
11 min into the jet through the spouting port at a flow rate of 4 L/min. In
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El-Naas, Munz, and Ajersch
Fig, 7. The effect of hydrogen addition on the rate of reaction. Carbon to calcium oxide molar
ratio was 3:1 and plasma gas flow rate was 40 L/min.
the second run, the current was lowered from 240 to 200 A at 17min,
decreasing the plasma power from 18 to 15 kW. Both methods resulted in
lowering the reaction zone temperature and consequently the rate of conversion as shown in Fig. 8 The effect immediately confirmed the fact that the
reaction was taking place in this zone. Also, the sensitivity of the rate to the
temperature change suggested that the global rate of reaction was controlled
by chemical reaction.
The jet temperature was lowered from 10,200 to 8600 K in the first case
and to 9500 K in the second case. The rate of reaction was lowered from
0.091 mol/min to about the same level (0.032 mol/min) for both cases
despite the difference in the predicted plasma jet temperature. This is mainly
due to the presence of methane as another source of carbon that is more
reactive than graphite. The reactivity of graphite and other sources of carbon
was discussed in a previous work.(19)
Solid-Phase Synthesis of Calcium Carbide in a Plasma Reactor
419
Fig. 8. The influence of sudden change of plasma jet temperature on the rate of reaction.
Carbon to calcium oxide molar ratio was 3:1 and plasma gas flow rate was 40 L/min.
3.3. Bed Stability
The fluid bed reactor, as described earlier, was divided into two zones:
the reaction zone at the bottom and the bed zone, where most particles were
present in the fluidized state. The reaction zone was created by positioning
the plasma torch at the bottom of the reactor. Although this arrangement
was effective in transferring plasma enthalpy to the bed materials, it can
result in a high-temperature zone where particles may melt and agglomerate.
When the reaction zone temperature is sufficiently high, partially reacted
particles soften and agglomerate when reaching a temperature near the melting point of calcium carbide. The large agglomerates tended to fall into the
bottom of the jet, where they combined and formed a cylindrical mass
around the jet. This occurred while the bed approached a temperature well
below the reaction temperature based on thermodynamic calculations. Stable
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EI-Naas, Munz, and Ajersch
fluidization and reaction were achieved, however, for most conditions
(except for 67% hydrogen) for periods up to 40 min. The stability of a run
was monitored by stable bed temperature and carbon monoxide concentration. The bed materials collected at the end of each stable experiment showed
little agglomeration and no melting. The solids seemed to be well mixed and
no segregation was observed. It is worth noting at this point that in a
continuous plasma process, the reactor will be run in a steady state at a
lower temperature. This eliminates the problems associated with melting and
agglomeration and results in high conversions.
3.4. Effect of CaO Particle Size
Calcium oxide powder had particle sizes ranging from 53 to 1100 um.
This range was divided into two portions in order to investigate the effect
of particle size on the rate of formation of calcium carbide. The first portion
contained particles greater than 53 and less than 425 um and had a mean
particle diameter of 150 um. Particles greater than 425 um and less than
1100 um were included in the second portion and had a mean particle size
of 600 um. Each portion was reacted with the graphite at a plasma power
of 16 kW. A plot for conversion vs. time for the two cases is shown in Fig.
9. Smaller particles exhibited a higher rate of reaction, due to the greater
surface area. However, the difference in reaction rate was not significant
compared to the difference in particle size (0.048 mol/min for 150 um and
0.039 mol/min for 60 um). For the reaction of spherical particles, the ratio
of reaction times needed to achieve a given conversion can be related to the
ratio of particle sizes as follows
where R1 and R2 are the radii of particles having the same conversion at
different times t1 and t2 respectively. The value of the exponent n may be
used to infer the controlling mechanism; it is equal to 2 for diffusion control,
1.5-2 for film diffusion control, and 1 for chemical reaction control.(20) For
the calcium oxide particles used in this study, the value of n is less than
unity as shown in Fig. 9. In a chemical reaction control mechanism, particle
size affects the rate through surface area. Clearly, the smaller oxide particles
have larger surface area for reaction. However, because of the high porosity
of calcium oxide, the effect of lowering particle size on surface area is minor
and, consequently, the effect on the rate is small.
Solid-Phase Synthesis of Calcium Carbide in a Plasma Reactor
421
Fig. 9. The effect of calcium oxide particle size on the reaction rate. Hydrogen concentration
was 45% and plasma power was 16kW. Carbon to calcium oxide molar ratio was 3:1 and
plasma gas flow rate was 40 L/min.
3.5. Product Analysis
3.5.7. Product Identification
The bed materials were examined visually after every experimental run
and samples were taken for analysis. In all experiments, except for pure
argon, the solid materials were black in color and no white solids were
observed. For the lowest power (0% H2), however, the bed contained some
grayish, white solids. This was mainly due to the low conversion for this
plasma condition. Samples of the solid product were reacted with water to
determine the calcium carbide content of the solid product (conversion).
Details of this procedure and other analytical techniques can be found
elsewhere.(21) X-ray diffraction analyses of the product were compared with
those of a standard calcium carbide sample. The samples were pulverized
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El-Naas, Munz, and Ajersch
to very fine powder to facilitate the analysis. The grinding and the exposure
of the powder to moisture in the atmosphere during the analysis resulted in
converting the carbide into calcium hydroxide. Thus, X-ray diffraction for
both the solid product and the standard sample showed only calcium oxide
and calcium hydroxide.
3.5.2. Microscopic Analysis
Microscopic analyses of the solid reactants and products were carried
out to examine the product morphology. Cross sections of particles were
examined and elemental spot analysis for calcium, carbon, and oxygen was
determined. Also, representative particles of unreacted and partially reacted
graphite and calcium oxide particles were mapped to determine the relative
distribution of calcium, carbon, and oxygen. It should be noted here that
for every product sample about one hundred particles were scanned, but
only a few were chosen for mapping. All particles examined had similar
morphology and indicated that all particles in a specific experiment reacted
to about the same extent.
Mapping of the different elements proved to be an effective tool in
determining the distribution of calcium, carbon, and oxygen across the unreacted and the partially reacted particles. The relative intensity of each element detected is indicated by the brightness of the image as the particle is
scanned. Due to the presence of carbon and oxygen in the mounting resin
(polymer), the backgrounds also show both of these elements.
Maps for a partially reacted graphite particle (Fig. 10) indicate that the
particle is subjected to a topochemical, shrinking core-type reaction. In the
carbon map (Fig. 10A), the rim is darker than the rest of the particle,
indicating less carbon is present at the rim of the particle. On the other
hand, in the calcium map (Fig. 10B) the rim is brighter, indicating that the
outer edge of the particle has more calcium. The lack of carbon in the rim
indicates that it is not calcium carbide. Spot analysis at different points in
the rim showed that it contained oxygen and calcium in an atomic ratio of
about 2 to 1. This implies that the outer edge of the particle has hydrated
to calcium hydroxide, which is formed as a result of the following reaction
Thus, carbon in the calcium carbide layer around the particle was removed
as acetylene. This was also observed for partially reacted calcium oxide
particles as shown in Fig. 11. Calcium carbide, therefore, had formed at the
surface of both reactants.
The microscopic analysis indicated that the formation of calcium carbide preceded according to the shrinking core model. The formation of
Solid-Phase Synthesis of Calcium Carbide in a Plasma Reactor
423
Fig. 10A. Carbon map for a partially reacted graphite particle.
calcium carbide on the graphite particles occurs through the reaction of
calcium vapor and carbon according to Eq. (3). This reaction is also believed
to be responsible for the formation of calcium carbide on the calcium oxide
particles by the reaction of calcium vapor and the carbon diffused into the
oxide particles. Calcium carbide can also form on the surface of the oxide
particles by the decomposition of the interstate compound (CaC3O) proposed by Muller.(17) It is difficult to state, however, which mechanism is
more important for the formation of calcium carbide on the calcium oxide
particles.
3.6. Product Decomposition
Previous studies of the solid-phase formation of calcium carbide showed
that calcium carbide decomposed according to the reverse of reaction (3),
and that the rate was zero order and increased with temperature.(13) The
decomposition occurred even at atmospheric pressure as reported by Mu
and Hard(3) and was slowed down by lowering the partial pressure of carbon
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El-Naas, Munz, and Ajersch
Fig. 10B. Calcium map for a partially reacted graphite particle.
monoxide. Brookes et al.(22) stated that the decomposition led to the formation of carbon and calcium vapor. The latter reacted with carbon monoxide
(2), deposited calcium oxide, and carbon on cooler surfaces as a gray dust.
The researchers also observed a carbide-free carbon ring on the outside of
the product layer. In the present study, it was rather difficult to confirm the
decomposition of calcium carbide. Although gray dust was observed on the
walls of the upper part of the disengaging section and the filter, no carbon
layers were observed on the partially reacted particles. Microscopic analysis,
as discussed in the preceding section, would clearly detect the presence of
any carbon around the particles, but no carbon was found around any
partially reacted graphite or calcium oxide particles. It is possible, nevertheless, that decomposition has occurred and that the carbon ring around the
particles was stripped off by attrition due to particle movement in the bed.
The extent of the decomposition, however, is expected to be minor due
to the low carbon monoxide partial pressure, which tends to hamper the
decomposition of calcium carbide.
Solid-Phase Synthesis of Calcium Carbide in a Plasma Reactor
425
Fig. 11 A. Carbon map for a partially reacted calcium oxide particle.
4. CONCLUSIONS
A new plasma spout-fluid bed process for the synthesis of calcium carbide was investigated. Calcium carbide can be produced in a granular form
by the solid-phase reaction of carbon and calcium oxide.
The spout-fluid bed reactor was found to have two different zones: a
high-temperature plasma reaction zone and a well-mixed isothermal bed
zone. The experimental results showed that the reaction took place in the
reaction zone and that conversion to calcium carbide increased linearly with
reaction time.
The rate of conversion to carbon monoxide was constant with time
for all conditions and increased exponentially with increasing plasma jet
temperature, indicating that chemical reaction was the controlling
mechanism.
Microscopic analysis of the solid product showed that calcium carbide
was formed around both graphite and calcium oxide particles, indicating
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El-Naas, Munz, and Ajersch
Fig. 11B. Calcium map for a partially reacted calcium oxide particle.
that the carbon-calcium vapor reaction took place at the surface of both
free carbon and the carbon diffused into the oxide.
Limitations with the present experimental apparatus made it difficult
to achieve conversions beyond 30% due to the melting and agglomeration
of particles in the plasma jet zone. Higher conversions, however, can be
expected in a continuous plasma process where the reactor will be run in a
steady state and at a lower temperature thus eliminating the problems of
melting.
ACKNOWLEDGMENTS
The financial support of the Libyan Secretariat of Scientific Research
in the form of a scholarship to M. H. El-Naas, the Natural Sciences and
Engineering Research Council of Canada, and FCAR, Quebec, are gratefully
acknowledged.
Solid-Phase Synthesis of Calcium Carbide in a Plasma Reactor
427
REFERENCES
1. K. Baba and N. Shohata, "Manufacture of calcium carbide micropowders by highfrequency plasma method," Japanese patent, No. 63112409 (1988).
2. S. Eriksson, "Calcium carbide from powdered limestone or lime," Belgian patent, No.
897179 (1983).
3. J. J. Mu and R. A. Hard, "A rotary kiln process for making calcium carbide," Ind. Eng.
Chem. Res. 26, 2063-2069 (1987).
4. C. S. Kim, R. Baddour, J. Howard, and H. Meissner, "CaC2 production from coal or
hydrocarbons in a rotating-arc reactor," Ind. Eng. Chem. Process Des. Dev. 18, No. 2,
323-328, 1979.
5. W. M. Goldberger and J. H. Oxley, "Quenching the plasma reaction by means of the
fluidized bed," A.I.Ch.E.J. 9, 778-782 (1963).
6. J. Jurewicz, P. Proulx, and M. I. Boulos, "The plasma spouted bed reactor," Proceedings
of ISPC-7, Eindhoven, July 1985, Vol. I, pp. 243-248.
7. C. R. Wierenga and T. J. Morin, "Characterization of a plasma fluidized bed reactor,"
A.I.Ch.E. J. 35, 1555-1560 (1989).
8. G. Flamant, "Hydrodynamics and heat transfer in a plasma spouted bed reactor," Plasma
Chem. Plasma Process. 10, 71-85 (1990).
9. R. J. Munz and O. S. Mersereau, "A plasma spout-fluid bed for the recovery of vanadium
from vanadium ore," Chem. Eng. Sci. 45, 2489-2495 (1990).
10. C. W. Zhu, G. Y. Zhao, and V. Hlavacek, "A dc plasma-fluidized bed reactor for the
production of calcium carbide," J. Mater. Sci. 30, 2412-2419 (1995).
11. M. H. EL-Naas, R. J. Munz, and F. Ajersch, "Production of calcium carbide in a plasmajet fluid bed reactor," Proceedings of ISPC-12, August 1995, Minneapolis, Minnesota,
U.S.A., Vol. II, pp. 613-618.
12. N. Kameyama, Electrochemistry: Theory and Application, Vol. III-2, 1956, pp. 134-141.
13. H. Tagawa and H. Sugawara, "The kinetics of the formation of calcium carbide in solidsolid reaction," Bull. Chem. Soc. Jpn. 35, 1276-1279 (1962).
14. T. Mukaibo and Y. Yamanka, J. Chem. Soc. Jpn., Ind. Chem. Sec. 58, 1955. [Cited in
Tagawa and Sugawara, 1962.]
15. P. Hellmold and W. Gordziel, "Investigation of the particular reactions of CaC2. 2: Investigation of the formation of CaC2 from calcium oxide and carbon," Chem. Technol. 35, 297300 (1983).
16. M. B. Muller, "Structure, properties and reactions of CaO in burnt lime, Part I: Design
of a new model of burnt lime," Scand. J. Metall. 19, 64-70 (1990).
17. M. B. Muller, "Structure, properties and reactions of CaO in burnt lime, Part III: Composite reactions of CaO and C in solid and liquid state," Scand. J. Metall. 19, 210-217 (1990).
18. M. H. EL-Naas, R. J. Munz, and F. Ajersch, "Modelling of a plasma reactor for the
synthesis of calcium carbide," Can. Metall. Quart, (in press).
19. M. H. EL-Naas, F. Ajersch, and R. J. Munz, "Effect of carbon reactivity on plasma
synthesis of calcium carbide," Proceedings of the 35th Annual Conference of Metallurgists,
Montreal, Quebec, Canada, August, 1996.
20. C. Y. Wen, "Non-catalytic heterogeneous solid fluid reaction models", Ind. Eng. Chem.
60, No. 9, 34-52(1968).
21. M. H. EL-Naas, "Synthesis of calcium carbide in a plasma spout fluid bed," Ph.D. Thesis,
McGill University, 1996.
22. C. Brookes, C. E. Gall, and R. R. Hudgins, "A model for the formation of calcium carbide
in solid pellets," Can. J. Chem. Eng. 53, 527-535 (1975).